Need Help Identifying Engine Knock Source

[RoGuE]

I bought a 2005 Cadillac CTS off a friend for basically nothing (less than scrap price) due to an engine noise. I can't tell if it's rod knock or timing chain noise. It's a 3.6L so timing chains wouldn't be surprising. It has 184K miles and came with a stack of records showing meticulous oil changes. Anyone have any input on this? The rest of the car is in really good shape (along with new tires and brakes) so I'd like to get it fixed to resell or maybe use myself. I scanned it and it did show a cylinder 1 misfire code but that went away after driving it home.

Video with the noise:

 

[clinebarger]

Not a rod knock, Could very well be timing components.

Use OE parts & I highly recommend installing new cam phasers when doing chains.

 

[Lawnman23]

Does the noise change when engine is cold vs hot?

Noise increases linearly with rpm I imagine?

Could pull the beauty cover off and hold your hand on each valve cover to see which bank feels clankier.

 

[RoGuE]

Does the noise change when engine is cold vs hot?

Noise increases linearly with rpm I imagine?

Could pull the beauty cover off and hold your hand on each valve cover to see which bank feels clankier.

It's hard to say as I didn't want to run it too long to limit any possible damage. I didn't notice any change in the noise. Yes, it increased with RPM. It did seem to be more noisy on the driver side. Also, when I pulled the oil cap off while it was running, which is located on the driver side, I could hear the sound much louder through the oil fill hole. Don't know if that means anything but I wouldn't imagine a rod knock get a lot louder in that situation.

 

[mattd]

Definitely not rod knock. I second Chris with likely timing component noise. Pull it apart and have a look.

 

[wings&wheels]

I'll second (third?) the timing chains opinion. That sounds almost exactly like the engine that produced this:

 

[clinebarger]

This engine (LY7) is known for timing chain issues, Good maintenance would be only reason for the chains to make it almost 200,000 miles.

I am surprised it doesn't have cam/crank correlation DTC's though.

Not so sure this is a job for a DIY'er.....I've seen journeymen mechanics struggle with these!

Updated phasers may require different thickness thrust washers!!!

This is a later model FWD SUV, But dropping the engine/trans on a RWD application (CTS/ATS/SRX/G8/Camaro) is even faster.

 

[Marcozi]

Another reason to buy an inline 6 cylinder engine.

 

[addyguy]

Definitely timing chains - it’s too ‘light’ and ‘clattery’ to be rod knock.
There is a reason he sold it to you for scrap value - at 184k with shot timing chains that is all it is.
Sure, you can fix the motor, but at that mileage, how much other stuff needs to be done??

 

[RoGuE]

Ok, thanks everyone for confirming it is likely timing chains. It's kind of what I suspected before I even saw the car knowing the history of these GM 3.6L. I think the car still has some life left in it given it was so well maintained.

I don't think this is something I want to do myself. What would a shop charge to do this job?

 

[RoGuE]

So I brought it to a shop for a diagnostic and as expected they say the guides are worn and the chain is slapping around. However, they advised me not to repair this engine as it also has evidence of blowby and cylinder scoring. They suspect it was run low on oil at some point.

So now, it seems to need an engine. Is a used engine with low miles a bad idea? Should I look around for a rebuilt engine? How is Jasper regarded these days?

 

[mattd]

Stay as far away from jasper as possible. Absolute garbage.

It would either rebuild the one you have or a known good low mileage used engine, but keep it mind that will likely have the same problematic timing set.

 

[RoGuE]

Update:

So as I was calling around different shops for engine replacement quotes, one offered to give a second opinion. He came to the same conclusion that the chains were bad but there wasn't any kind of severe blowby that the other shop mentioned. He came back with a quote of about $4400....more than the car is really worth. So now it's in my garage and I'm going to be attempting it myself. I've wanted a project and now I've got one. I've got a space in the garage and I'll be able to take my time with it.

What timing set do you guys recommend? Cloyes vs Melling vs OEM? Should I replace the oil pump while I'm in there? And I researched on how to check if the cam phasers are functioning. Do I need the cam tool to hold them in place or is that optional?

 

[RoGuE]

Another update if anyone is interested. Finally got to pulling the timing cover and the issue was evident. The chain guide on the driver side bank slid down and the chain is just riding on the bare metal. The primary chain and the drive side bank feel pretty lose. The primary tensioner and passenger side tensioner both feel locked up and don't seem to have any movement.

Apparently this is not the first timing chain replacement...I see all Melling sprockets, guides, and oil pump. All of this matches an invoice I had in the paperwork (that I thought was just an estimate that was declined) that shows replacement of all that in July 2022 and about 15k miles ago. Goes to show what happens when you let the oil get low.

I planned on replacing the oil pump under the assumption it was original...should I still do that? The chain was riding on the aluminum of the guide on the driver side so it probably had some metal shavings. The oil looked pretty clear when I drained it but I haven't looked at the filter yet.